1. Field of the Invention
The present invention relates to an imaging device having a flexible printed board, and more particularly although not exclusively, an imaging device having a flexible printed board disposed in a lens barrel equipped with a movable member.
2. Description of the Related Art
There is a conventional collapsible lens barrel that includes a device for shifting an optical lens, which enables storing the optical lens in a camera body when a camera is not used and shifting the optical lens to a predetermined extended position when the camera is used.
Furthermore, there is a conventional zoom lens barrel that can shift a plurality of optical lens in an optic-axial direction to change a focal distance of a photographing lens.
Furthermore, there is a conventional lens barrel that has both collapsing and zooming capabilities.
According to one of such lens barrels, a diaphragm or a shutter is driven by an electromagnetic device and is arranged to shift back and forth in an optic-axial direction together with an optical lens. An electromagnetic driving section that shifts in the optic-axial direction must be electrically connected to a stationary camera controller equipped in the camera body. This is the reason why a flexible printed board is used to connect the electromagnetic driving section to the camera controller.
The flexible printed board can bend or flex to follow a displacement or shifting of the electromagnetic driving section and accordingly allows the electromagnetic driving section to shift to a desired position while maintaining electrical connection between the electromagnetic driving section and the camera controller.
In addition to a diaphragm or a shutter, an actuator for a vibration-correction lens barrel can be housed in a lens barrel. The actuator causes the lens to shift in a plane substantially perpendicular to an optical axis to cancel camera shake. A sensor measuring the temperature can be equipped in the lens barrel. The actuator and/or the sensor can be integrated with an optical group shifting in a lens barrel. Also in such cases, the actuator and/or the sensor can be connected via a flexible printed board to a camera controller of a camera body.
The length of a flexible printed board is determined considering both a most collapsed position and a most extended position of a lens barrel. Hence, the flexible printed board in the lens barrel is usually in a bent or deflected state and accordingly can produce a ghost on an image because the flexible printed board is possibly positioned in the vicinity of an imaging beam.
The cause or mechanism of such a ghost will be described with reference to FIG. 10.
FIG. 10 is a transversal cross-sectional view showing a conventional lens barrel in an intermediate state between a wide angle state and a telephoto state. A flexible printed board 101 shown in FIG. 10 is configured to electrically connect an electromagnetic driving source of a diaphragm and/or a shutter equipped in a lens barrel to a camera controller provided outside the lens barrel. Furthermore, FIG. 10 shows an imaging element 102 having an imaging plane, a first lens group 103, a second lens group 104, a third lens group 105, and a light beam 106.
As shown in FIG. 10, the light beam 106 passes through the first lens group 103 and the second lens group 104 while causing refractions in the first lens group 103 and the second lens group 104, respectively. According to the arrangement shown in FIG. 10, the light beam 106 can be reflected, depending on its incident angle, at the flexible printed board 101 bent in the lens barrel. Then, the light beam 106 can reach the imaging element 102 after passing through the third lens group 105. If a light source of the light beam coming from outside of a target area is bright enough, the light beam 106, including any reflection from the flexible printed board 101, can cause a ghost on a photographed image.
To reduce the occurrence of the light beam causing a ghost due to the above-described interference with the flexible printed board in the path passing through respective lenses before reaching the imaging element, there is no method other than eliminating the reflection of light from the flexible printed board. To this end, various methods have been discussed to reduce or eliminate an excessive length of the flexible printed board.
For example, Japanese Patent Laid-open Application No. 07-20370 discusses a method of moving back and forth a guide member guiding a flexible printed board in an optic-axial direction to eliminate or reduce the excessive length.
Furthermore, Japanese Patent Laid-open Application No. 2001-188289 discusses a guide roller around which a flexible printed board is wound, in which the guide roller is shifted back and forth in accordance with a back-and-forth shifting movement of a shutter unit connected to the flexible printed board so as to eliminate or reduce the excessive length.
However, according to the arrangement discussed in Japanese Patent Laid-open Application No. 07-20370, a space for allowing the guide member to move in the optic-axial direction must be secured. Thus, downsizing the lens barrel is difficult and facilitates the inclusion of a member for shifting the guide member. This fails to facilitate downsizing the lens barrel. Besides, an additional number of parts are required which increase the manufacturing cost.
Moreover, according to the arrangement discussed in Japanese Patent Laid-open Application No. 2001-188289, both the guide roller and a member for shifting the guide roller are required which increase the manufacturing cost. Furthermore, a moving space for the guide roller is required and accordingly downsizing the lens barrel is difficult.